Shoe bottom filler



Patented May 9, 1944 SHOE Bo'r'roM FILLER Howard M. Dodge and Russell J. Bush, Wabash, Ind., assignors to The General Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application October 5, 1939,

Serial No. 298,084

4 Claims.

This invention relates to improvements in shoe bottom fillers and particularly to shoe bottom fillers adapted to be easily spread at normal templeratures between the insole and outsole of a s e.

In the manufacture of shoes the space between the inner and outer sole and within the margin of the shoe uppers is usually filled with a compound consisting of a solid material such as cork, rubber sponge and the like which is granulated, or otherwise finely divided and which is thoroughly mixed with an adhesive binder. shoe-filling compounds may be divided into two classes, namely those fillers which are plastic in the cold state and which solidify by evaporation of a solvent and those fillers which must be ment with suitable comminuted materials. After the material is spread on the shoe bottom it is preferably coated with a concentrated solution of an accelerator or accelerator activator to cause curing of the rubber to take place without the necessary application of heat. The comminuted material may be cork or similar comminuted Such heated to melt the binding material so that the product is sufficiently fluid for application.

The cold type of filler obviously has many advantages in the process of manufacturing shoes, since it does not require a long time before it can be used and it is not necessary to keep it hot, but it has not come into general use because fillers heretofore prepared usually solidified in the container. when prepared for any length of time prior to their use, they were not sufficiently a shoe does not deform badly and alter its shape to the discomfort of the wearer of the shoe.

It is another object of this invention to provide a method of applying a cold plastic shoe filler to shoes so as to produce a solid but resilisolid but it has been found that shoe bottom fillers having much improved characteristics are obtained with a mixture, of comminuted cork, comminuted sponge and fibrous material, such as cotton linters and the like. The fibrous material, when held by films of rubber, aids in preventing the bunching of the material in the shoe to the discomfort of the wearer. It has been found that such fibers are more effective when the rubber films are in a vulcanized and less plastic state.

The comminuted sponge which is preferably a rubber sponge permits some of the rubber cement to migrate into its pores-and hence greatly improves the bond between the several ingredients,

acting as an anchoring ingredient which permitsthe strengthening action of the fibers to be most fully utilized. Other comminuted rubber 3. and fibrous materials, such as ground tire cartacky when wet, their drying time was much too ent product which does not change its shape during the wearing of the'shoe. 7

It is a further object of this invention to provide a shoe filler which maybe applied to shoe bottoms in a cold plastic state, which has a suffi casses, etc, are also desirable and may be used in place of the sponge and cotton to produce shoe bottom fillers having but slightly inferior characteristics. .The cork promotes lightness and resilience of the composition, effectively preventing substantialy shrinkage of the material when the solvent is dissipated. V,

The preferred binding material is a latex solvent cement, such as, that disclosed in the copending application Serial No. 293,103 of Russell J. Bush, filed September 1, 1939, now Patent No. 2,304,678 issued December 8, 19%2. 7 As there set forth, the cement has a continuous phase of rubber swelledby rubber solvent and a disperse phase of water or other non-rubber solvent. It may .be prepared by intimately mixing a rubber latex and a rubber solvent with the aid of a carrier medium such as alcohol, acetone, etc., to produce a gel structure having the water from the latex dispersed in the rubber cement. A somewhat similar cement may also be prepared by intensely beating latex and solvent together without the aid of sucha carrier. A cement prepared by beating water or other liquid which is not a rubber solvent or miscible therewith into any viscous rubber cement so as to produce a homogeneous mixture, may also be used. Cements prepared from latex are preferred however for the reason that the high strength, which is occasioned by the unbrokendown molecular structure of the latex, enables the use of smaller quantities of rubber, and any tendency for coagulation of the material in a closed container is diminished.

The volatile solvent in the cement shortens the time required for drying of the cement and the water appears to prevent the absorption by the comminuted solids of sufficient of the solvent from. the cement to cause coagulation of the mixture in closed containers.

To provide increased tackiness so that the shoe filler will readily adhere to the leather while wet, it is preferred to add rosin or other tack producing material, such as, for example, coumarone-indene resins, hydrogenated rosin, etc., to the cement. which is preferably of the unsaponified type also increases the cohesion of the solidified filler so that the rubber adheres more firmly to the comminuted solids and a firmer material is obtained. Rosin is a particularly effective tack producer and should ordinarily be added in amounts of about 2 to about 4 or 5% of the cement or in a sufficient quantity to saturate the solvent. Good compounds, however, have been produced with less rosin but tackiness decreases rapidly.

Rosin and similar unsaponified tack producers which are insoluble in water have been found to be considerably more effective in producing the desired tackiness in the binding materials used according to this invention than the tack producing materials which are soluble in aqueous solutions and which are usually used in cement. This is probably because of the fact that in the preferred shoe bottom fillers of this invention, the rubber and solvent are in the continuous phase and materials which are soluble in the dispersed aqueous phase of the cement do not come in contact with surfaces to which the cements are applied and hence are of less value.

In the preparation of the shoe fillers, a sufficient amount of rubber solvent is added to the comminuted solids to saturate them with liquid before the addition of the rubber cement, so that the solid particles will have less tendency to absorb the solvent from the cement and cause thickening in the container prior to use. A comparatively thick cement may then be mixed with these solid ingredients to produce a shoe filler which retains its initial consistency for an in definite time.

While the quantities of the respective ingredients may be varied considerably, it has been found that the desirable characteristics are obtained with shoe fillers having about 1-3 volumes of comminuted cork, A to 1%; volumes of comminuted rubber sponge, or equivalent rubber material, around .05 to .2 volume of fibrous material, such as cotton linters, and sufficient tacky latex-solvent cement having a rubber content of 5. to 20%, to form a mix of the desired plasticity.

The following examples illustrate the shoe fillers of this invention.

Example I The tack producing material minuted cork and about 1 volume of ground scrap rubber sponge which contained about 15% of cotton linters. The comminuted cork and sponge had previously been mixed with about e volume of rubber solvent to prevent excess absorption of the solvent from the cement and to prevent subsequent change in viscosity of the filler. To facilitate the spreading of the material and to prevent the material from sticking to the spatula, a small amount, such as about /4 or /5 volume, of a saturated solution of paraflin or other wax in a suitable solvent, such as carbon tetrachloride, was added to the mix.

The material thus produced is extremely tacky when applied to leather and may be stored indefinitely in closed containers without solidifying.

In the application of the shoe bottom filler,

it is preferred to provide means for vulcanizing the rubber constituent so as to more effectively prevent undesirable bunching of the filler when, the shoe is worn. If it is not necessary to have a comparatively short drying time, this may be accomplished by the use of a prevulcanized aqueous latex cement which is sufficiently diluted to prevent gelation. Usually, however, the drying or setting time of the material must be short and a more volatile solvent must be used. Such cements have a continuous rubber phase and have more tendency to gel in the vulcanized condition. It is desirable, therefore, to add vulcan izing ingredients to the cement and vulcanize them after the shoe filler has been placed in the shoe bottom. Such vulcanization may be effected by incorporating vulcanizing ingredients in the cement and coating the filler after it has been placed in a shoe bottom with a rapidly acting accelerator which is preferably in solution. The Shoe bottom fillers of this invention are relatively porous and it has now been found that an accelerator may be incorporated in the uncured rubber of porous articles generally by applying a sufficient amount of a solution of an accelerator to one or more of their exposed surfaces. Even in comparatively thick porous articles the accelerator will migrate through the whole mass of rubber films and by selecting appropriate vulcanizing accelerators in accordance with data available to those skilled in the art, the compound may be cured at room temperature. By the use of the vulcanizing type of accelerators such vulcanization of the uncured rubber in porous articles may be accomplished even though it contained no curing agents.

Example II A non-inflammable cement was prepared by adding 1 gal. of gasoline, 1 gallons of carbon tetrachloride containing 5% of dissolved rosin and pint of alcohol, to 45 oz. of latex containing 60% rubber solids, and slightly agitating the mix. The latex cement was compounded with 2% of sulphur, 4% of zinc oxide and 4% of dibutyl amine, all percentages being'based on the rubber content. This was mixed intimately with the comminuted solids set forth in Example I to form the bottom filler. This shoe filler was spread in shoe bottoms and before the application of the shoe sole, the exposed surface of the filler was also painted with a strong solution or dispersion of the zinc butyl xanthate which cooperates with the dibutyl amine to produce a high rate of cure.

After about 3 or 4 days at room temperature the rubber in the bottom filler was found to be substantially vulcanized to produce a bottom filler which did not bunch in shoe bottoms to any extent.

Although the filling material of this invention has been described as a shoe bottom filler, it is to be understood that it is useful for other purposes such as floors, insulation, etc, where an easily spreadable porous rubber containing composition is desired. The particular methods and compounds disclosed and the procedure set forth are merely illustrative, and are presented for the purposes of explanation and illustration, and various equivalents of the methods can be used and modifications of the procedure made without departing from the spirit of our invention.

What we claim is:

1. A process for preparing shoe filling compounds of an easily spreadable consistency and which may be stored in closed containers for relatively long periods of time without solidifying and without appreciably thickening, which comprises the steps of first mixing suitably comminuted, absorptive, solid filling materials with a substantial amount of a rubber solvent to reduce their absorptive capacity and then mixing the said comminuted solids with a rubber cement having a continuous phase of rubber swollen by solvent, a disperse phase of water and containing a dissolved wax and an unsaponified tack producing material.

2. A normally plastic shoe bottom filler which is easily spread at normal temperatures and which retains a spreadable consistency in closed containers for an indefinite period, comprising comminuted cork, fibers, rosin, and a rubber cement; having a continuous phase of rubber swollen by solvent and a disperse phase of a liquid which is not a rubber solvent, said cement also containing a dissolved wax which facilitates spreading of the normally plastic composition.

3. A shoe bottom filler which is easily spreadable at normal temperatures and which retains a spreadable consistency in closed containers for an indefinite period, comprising comminuted cork, fibers, rosin, and a cement of rubber latex, having the unmasticated rubber particles swollen by a rubber solvent to form a continuous phase of rubber and a disperse phase of water, said cement containing vulcanizing ingredients for the rubber and a dissolved wax which facilitates spreading of the composition.

4. A shoe bottom filler which is easily spreadable at normal temperatures and which retains a spreadable consistency in closed containers for an indefinite period, comprising comminuted cork, fibers, an unsaponified tack producing material, and a cement of rubber latex, having the unmasticated rubber particles swollen by a rubber solvent to form a continuous phase of rubber and a disperse phase of water, said cement containing vulcanizing ingredients for the rubber and a dissolved wax which facilitates spreading of the composition.

HOWARD M. DODGE. RUSSELL J. BUSH. 

